1. Field of the Invention
The present invention relates to improvements in a pre-wind type camera which employs a film having a magnetic storage portion and which comprises: a magnetic head for writing to and/or reading from the magnetic storage portion provided on the film; a pressing element for pressing the magnetic head and the storage portion to touch each other; and a motor for conveying the film.
The above mentioned pre-wind type camera refers to a camera which winds the entire film on a film-winding spool and then rewinds the film one frame at a time.
2. Description of the Related Art
In a conventional film-loading method, a film is loaded by engaging a tip portion, i.e. the leader, of the film protruding from the film cartridge with a sprocket or winding spool and then by rotating the sprocket or the winding spool. In such a method, a user has to take the trouble of setting the leader of the film in a designated position. If the leader is not set in the proper position, the film may not be loaded properly. Further, when setting the leader, the user may draw out and expose the film more than is necessary.
To solve this problem, U.S. Pat. No. 4,834,306 discloses a new type film cartridge which is described below and is illustrated in FIGS. 10 to 12.
As shown in the FIGS. 10 to 12, a slit 37 is provided to guide the film out of the cartridge. The film 34 is coiled around a film spool 38 with one of its ends fixed to a recess 38a provided on the film spool 38. Stopper elements 39 having restricting portions 39a are provided concentrically with the film spool 38. The restricting portions 39a keep the outermost layer of the film 34 from radially expanding and touching the inside wall 35a of the film cartridge 35. Releasing elements 40 are provided for deforming portions of the stopper elements 39 to continuously release the outermost layer of the film from radial restriction by the stopper elements 39. The released portion of the film 34 is guided to the slit 37 by guiding elements 41. In this construction, the film 34 can be pushed out of the cartridge 35 by rotating the film spool 38 in the uncoiling direction, since the outermost layer of the film 34 tends to expand by the uncoiling rotation of the spool 38 and presses the stopper elements 39 firmly enough to prohibit sliding between the stopper elements 39 and the outermost layer of the film 34.
In using this kind of cartridge (referred to as a "thrust-type film cartridge"), the user does not have to touch the leader of the film 34 when loading the film 34 in the camera. After the film cartridge 35 is set in the camera, the film 34 is forced out of the film cartridge by the rotation of the film spool 38 transmitted from a fork of the camera until the tip portion of the film 34 hooks or curls around the film spool in the camera. Then the film spool 38 of the camera winds and draws the film 34 to complete the film loading operation.
U.S. Pat. No. 4,864,332 discloses a camera wherein a magnetic head writes photographic data, such as shutter speed, aperture, date and title into a magnetic storage portion provided in the film and reads out the data upon request.
Also, Wo90/04203 (PCT/US89/04343) discloses a camera wherein a magnetic head writes into a magnetic storage portion of the film only when one frame has been exposed and the film is being advanced to the next frame.
For accurate writing and/or reading in such a camera, the magnetic head and the storage portion of the film must be pressed to securely touch each other when the head writes to and/or reads from the storage portion. Accordingly, a film-pressing means such as a pressing pad must be provided on the other side of the film from the magnetic head. When the thrust-type film cartridge is employed to accommodate a film having a magnetic storage portion, there exist the following problems:
1) In a construction where the film-pressing means is always pressed to the head by an elastic element such as a spring: PA1 2) In a construction where the film-pressing means or the magnetic head is designed to be moved by a motor or the like in the direction of the thickness of the film so that the film-pressing means or the magnetic head stays away from the path of the film until the tip of the film has passed thereby:
when the film is being pushed out for loading, the tip of the film may be stopped at the film-pressing means or the magnetic head. In such a case, loading the film is no longer possible. PA2 installing another drive source such as a motor raises costs. Also, a complicated electric circuit is required due to the complicated timing involved in pressing the film onto the head.
The magnetic storage portion of the film extends in the lengthwise direction thereof at a predetermined position. To respond to increasing information to be written and/or read, the magnetic head must be precisely positioned at the predetermined position.
The inventor has made an application for a camera comprising a film platen which has a magnetic head fixed thereto and a guide portion and which is movable substantially perpendicular to the film surface and is rotatable on a plane parallel with the film surface, and wherein the film platen is pressed by an elastic element such as a spring so that the guide portion pressingly touches a film edge and thus a magnetic storage portion of the film is precisely positioned with respect to the magnetic head.
When the thrust-type film cartridge accommodating a film having a magnetic storage portion is set in such a camera as constructed above and the film is pushed out for automatic loading, the film tip pushes the guide portion against the restoration force of the elastic element and then the guiding portion abuts against an edge surface of the film. However, there is a possibility that the film may be bent or caught at the guide portion when film is pushed against the force of the elastic element. In such a case, the film can no longer be pushed out.